High-power lasers are used in many cutting, etching, annealing, welding, drilling, and soldering applications. An advantage to these systems is the precision with which cuts can be made and recesses etched into a wide variety of materials.
One challenge in implementing high-precision laser-based processing systems is determining the height or depth of a feature as it is formed. Material anisotropy, or even ordinary compositional variations across a nominally uniform material, can affect the amount of material removed by a laser at a given power level. Without real-time knowledge of feature depth or height during processing, and feedback capability to alter the beam in response thereto, it is impossible to guarantee precise dimensions that do not vary across the feature particularly if the feature extends across a considerable (e.g., more than a few microns) length, since the more material that is processed, the greater will be the likelihood of encountering compositional variations that affect material response.